I agree with the OP.
If a DLC alter the balance of the game, then that has to be balanced with the whole game, in it's current and any future itteration.
Let's say they chose to add a DLC that flesh out the classical era, a DLC that added 6 new naval units all across the tech tree, and a DLC that extended the future era.
The work to keep a balanced game would be enormous, considering the 4 DLC that now optionally add something to the game.
The game AI would have to be tuned to all of this.
So my oppinion is that DLC that alter the base features of the game is a bad idea, but DLC like extra civ that does not alter the base gameplay of all other civs are just fine.
Leave the other changes to the modders, or even better help the modders even more.
If a DLC alter the balance of the game, then that has to be balanced with the whole game, in it's current and any future itteration.
Let's say they chose to add a DLC that flesh out the classical era, a DLC that added 6 new naval units all across the tech tree, and a DLC that extended the future era.
The work to keep a balanced game would be enormous, considering the 4 DLC that now optionally add something to the game.
The game AI would have to be tuned to all of this.
So my oppinion is that DLC that alter the base features of the game is a bad idea, but DLC like extra civ that does not alter the base gameplay of all other civs are just fine.
Leave the other changes to the modders, or even better help the modders even more.